Phospholipase C (PLC) belongs to a family of enzymes, also known as disulfide isomerases, which play an important role in mediating signal transduction pathways. Many extracellular signaling molecules including hormones, growth factors, neurotransmitters, and immunoglobulin bind to their respective cell surface receptors and activate PLCS. Activated PLCs then catalyze the hydrolysis of phosphatidyl-inositol-4,5-bisphosphate (PIP2), a component of the plasma membrane, to produce diacylglycerol and inositol 1,4,5-trisphosphate (IP3).
In their respective biochemical pathways, IP3 and diacylglycerol serve as second messengers and trigger a series of intracellular responses. IP3 induces the release of calcium from internal cellular storage, and diacylglycerol activates protein kinase C (PKC). Both pathways are part of transmembrane signal transduction mechanisms, which regulate numerous cellular processes, including secretion, neural activity, metabolism, and proliferation.
PLC molecules have been found in a broad spectrum of organisms including bacteria, simple eukaryotes, plants and animals (Munnik et al., Biochim. Biophys. Acta. 1389:222-272, (1998)). Several distinct isoforms of PLC have been identified in animals and are categorized as PLC-beta, PLC-gamma, and PLC-delta. Subtypes are designated by adding Arabic numbers after the Greek letters, e.g., PLC-beta-1. PLCs have a molecular mass of 62-68 kDa, and their amino acid sequences show two regions of significant similarity.